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1.
Zn 2GeO 4/N‐doped graphene nanocomposites have been synthesized through a fast microwave‐assisted route on a large scale. The resulting nanohybrids are comprised of Zn 2GeO 4 nanorods that are well‐embedded in N‐doped graphene sheets by in situ reducing and doping. Importantly, the N‐doped graphene sheets serve as elastic networks to disperse and electrically wire together the Zn 2GeO 4 nanorods, thereby effectively relieving the volume‐expansion/contraction and aggregation of the nanoparticles during charge and discharge processes. We demonstrate that an electrode that is made of the as‐formed Zn 2GeO 4/N‐doped graphene nanocomposite exhibits high capacity (1463 mAh g ?1 at a current density of 100 mA g ?1), good cyclability, and excellent rate capability (531 mAh g ?1 at a current density of 3200 mA g ?1). Its superior lithium‐storage performance could be related to a synergistic effect of the unique nanostructured hybrid, in which the Zn 2GeO 4 nanorods are well‐stabilized by the high electronic conduction and flexibility of N‐doped graphene sheets. This work offers an effective strategy for the fabrication of functionalized ternary‐oxide‐based composites as high‐performance electrode materials that involve structural conversion and transformation. 相似文献
2.
Nanostructured α‐Fe 2O 3 with and without fluorine substitution were successfully obtained by a green route, that is, microwave irradiation. The hematite phase materials were evaluated as a high‐performance electrode material in a hybrid supercapacitor configuration along with activated carbon (AC). The presence of fluorine was confirmed through X‐ray photoelectron spectroscopy and transmission electron microscopy. Fluorine‐doped Fe 2O 3 (F‐Fe 2O 3) exhibits an enhanced pseudocapacitive performance compared to that of the bare hematite phase. The F‐Fe 2O 3/AC cell delivered a specific capacitance of 71 F g ?1 at a current density of 2.25 A g ?1 and retained approximately 90 % of its initial capacitance after 15 000 cycles. Furthermore, the F‐Fe 2O 3/AC cell showed a very high energy density of about 28 W h kg ?1 compared to bare hematite phase (~9 W h kg ?1). These data clearly reveal that the electrochemical performance of Fe 2O 3 can be improved by fluorine doping, thereby dramatically improving the energy density of the system. 相似文献
3.
Three‐dimensional hierarchical porous graphene/carbon composite was successfully synthesized from a solution of graphene oxide and a phenolic resin by using a facile and efficient method. The morphology, structure, and surface property of the composite were investigated intensively by a variety of means such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). It is found that graphene serves as a scaffold to form a hierarchical pore texture in the composite, resulting in its superhigh surface area of 2034 m 2g ?1, thin macropore wall, and high conductivity (152 S m ?1). As evidenced by electrochemical measurements in both EMImBF 4 ionic liquid and KOH electrolyte, the composite exhibits ideal capacitive behavior, high capacitance, and excellent rate performance due to its unique structure. In EMImBF 4, the composite has a high energy density of up to 50.1 Wh kg ?1 and also possesses quite stable cycling stability at 100 °C, suggesting its promising application in high‐temperature supercapacitors. In KOH electrolyte, the specific capacitance of this composite can reach up to an unprecedented value of 186.5 F g ?1, even at a very high current density of 50 A g ?1, suggesting its prosperous application in high‐power applications. 相似文献
4.
Heteroatom‐doped carbon materials have been widely used in energy storage and conversion such as supercapacitors and electrocatalysts. In this work, L‐asparagine (Asn), an amino acid derivative, has been used as a doping agent to prepare nitrogen‐ doped reduced graphene oxide gels (N‐GAs). The 3D interconnected structure gives rise to the superior electrochemical properties for supercapacitor and electrocatalytic oxygen reduction reaction (ORR). The N‐GA‐4 (the mass ratio of Asn to graphene oxide (GO) is 4 : 1 by hydrothermal method) electrode shows the capacitance of 291.6 F·g –1 at 0.5 A·g –1. Meanwhile, the assembled symmetric supercapacitor achieves a maximum energy density of 23.8 Wh· kg –1 when the power density is 451.2 W·kg –1, and demonstrates an ultralong cycling life that the retention of capacitance is 99.3% after 80000 cycles. What's more, the annealed aerogel N‐GA‐4‐900 exhibits an onset potential ( Eonset) of 0.95 V, half wave potential ( E1/2) of 0.84 V (vs. RHE) and the oxygen reduction current density of 5.5 mA·cm –2 at 0.1 V with nearly four‐electron transfer, which are superior to commercial Pt/C. This work offers a new insight into the synthesis and applications of N‐GAs materials towards high performance in supercapacitors and ORR. 相似文献
5.
Three‐dimensional, vertically aligned MnO/nitrogen‐doped graphene (3D MnO/N‐Gr) walls were prepared through facile solution‐phase synthesis followed by thermal treatment. Polyvinylpyrrolidone (PVP) was strategically added to generate cross‐links to simultaneously form 3D wall structures and to incorporate nitrogen atoms into the graphene network. The unique wall features of the as‐prepared 3D MnO/N‐Gr hybirdes provide a large surface area (91.516 m 2 g ?1) and allow for rapid diffusion of the ion electrolyte, resulting in a high specific capacitance of 378 F g ?1 at 0.25 A g ?1 and an excellent charge/discharge stability (93.7 % capacity retention after 8000 cycles) in aqueous 1 m Na 2SO 4 solution as electrolyte. Moreover, the symmetric supercapacitors that were rationally designed by using 3D MnO/N‐Gr hybrids exhibit outstanding electrochemical performance in an organic electrolyte with an energy density of 90.6 Wh kg ?1 and a power density of 437.5 W kg ?1. 相似文献
6.
Understanding the impact of the defects/defect density of electrocatalysts on the activity in the triiodide (I 3?) reduction reaction of dye‐sensitized solar cells (DSSCs) is indispensable for the design and construction of high‐efficiency counter electrodes (CEs). Active‐site‐enriched selenium‐doped graphene (SeG) was crafted by ball‐milling followed by high‐temperature annealing to yield abundant edge sites and fully activated basal planes. The density of defects within SeG can be tuned by adjusting the annealing temperature. The sample synthesized at an annealing temperature of 900 °C exhibited a superior response to the I 3? reduction with a high conversion efficiency of 8.42 %, outperforming the Pt reference (7.88 %). Improved stability is also observed. DFT calculations showed the high catalytic activity of SeG over pure graphene is a result of the reduced ionization energy owing to incorporation of Se species, facilitating electron transfer at the electrode–electrolyte interface. 相似文献
7.
The manufacture of single-atom transition metal-doping carbon nanocomposites as electrode materials is crucial for electrochemical energy storage with high energy and power density. However, the simple strategy for preparation of such active materials with controlled structure remains a great challenge. Here, cobalt-doped carbon nanocomposites (Co-POM/rGO) were synthesized successfully by deposition of Anderson-type polyoxometalate (POM) on the surface of reduced graphene oxide (rGO) aerogel via one-pot hydrothermal treatment. The resulting Co-POM/rGO possesses three-dimensional graphene-based frameworks with hierarchical porous structure, high surface area and uniform single-atom metal doping. These intriguing features render Co-POM/rGO to be a promising electrode for applications in electrochemical energy storage. As an electrode material of a supercapacitor, Co-POM/rGO shows high-performance electrochemical energy storage (211.3 F g?1 at 0.5 A g?1). Furthermore, the solid-state asymmetric supercapacitor (ASC) device, using Co-POM/rGO as a positive electrode, exhibits the outstanding energy density of 37.6 Wh kg?1 at a power density of 500 W kg?1, and high capacitance retention of 95.2% after 5000 charge–discharge cycles. These results indicate that the proposed strategy for rational design of single-atom-metal doped carbon nanocomposites for flexible ASC devices with excellent capacitive properties. 相似文献
8.
Porous carbons (PC) were prepared from a waste biomass named chestnut shell via a two‐step method involving carbonization and KOH activation. The morphology, pore structure and surface chemical properties were investigated by scanning electron microscopy (SEM), N 2 sorption, Raman spectroscopy, X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The carbons have been evaluated as the electrode materials for supercapacitors by a two‐electrode system in 6 mol/L KOH electrolyte. Benefiting from the porous texture, high surface area and high oxygen content, the PCs derived from chestnut shell have exhibited high specific capacitance of 198.2 (PC‐1), 217.2 (PC‐2) and 238.2 F·g ?1 (PC‐3) at a current density of 0.1 A·g ?1, good rate capability of 55.7%, 56.6% and 54.9% in a range of 0.1–20 A·g ?1 and high energy density of 5.6, 6.1 and 6.7 Wh·kg ?1, respectively. This is believed to be due to electric double layer capacitance induced by the abundant micropores and extra pseudo‐capacitance generated by oxygen‐containing groups. At a power density of 9000 Wh·kg ?1, the energy density is 3.1, 3.5 and 3.7 Wh·kg ?1 for PC‐1, PC‐2 and PC‐3, respectively, demonstrating the potential of the carbons derived from chestnut shells in energy storage devices. 相似文献
9.
The ionic conductivity and small size of the hydrogen ion make it an ideal charge carrier for hydrogen‐ion energy storage (HES); however, high‐voltage two‐electrode configurations are difficult to construct as the result of the lack of efficient cathodic energy storage. Herein, the high potential fast anionic redox at the cathode of reduced graphene oxide (rGO) was applied by introducing redox additive electrolytes. By coupling the storing hydrogen ion in the Ti 3C 2T x at the anode, a HES with a voltage of 1.8 V and a plateau voltage at 1.2 V was constructed. Compared with 2.2 Wh kg ?1 for the low‐voltage Ti 3C 2T x//Ti 3C 2T x, the specific energy of asymmetric rGO//Ti 3C 2T x reaches 34.4 Wh kg ?1. Furthermore, it possesses an energy density of 23.7 Wh kg ?1 at high power density of 22.5 kW kg ?1. Thus, this study provides a novel guideline for constructing high‐voltage fast HES full cells. 相似文献
10.
Germanium quantum dots embedded in a nitrogen‐doped graphene matrix with a sponge‐like architecture (Ge/GN sponge) are prepared through a simple and scalable synthetic method, involving freeze drying to obtain the Ge(OH) 4/graphene oxide (GO) precursor and subsequent heat reduction treatment. Upon application as an anode for the lithium‐ion battery (LIB), the Ge/GN sponge exhibits a high discharge capacity compared with previously reported N‐doped graphene. The electrode with the as‐synthesized Ge/GN sponge can deliver a capacity of 1258 mAh g ?1 even after 50 charge/discharge cycles. This improved electrochemical performance can be attributed to the pore memory effect and highly conductive N‐doping GN matrix from the unique sponge‐like structure. 相似文献
11.
A hierarchical hollow hybrid composite, namely, MnO 2 nanosheets grown on nitrogen‐doped hollow carbon shells (NHCSs@MnO 2), was synthesized by a facile in situ growth process followed by calcination. The composite has a high surface area (251 m 2g ?1) and mesopores (4.5 nm in diameter), which can efficiently facilitate transport during electrochemical cycling. Owing to the synergistic effect of NHCSs and MnO 2, the composite shows a high specific capacitance of 306 F g ?1, good rate capability, and an excellent cycling stability of 95.2 % after 5000 cycles at a high current density of 8 A g ?1. More importantly, an asymmetric supercapacitor (ASC) assembled by using NHCSs@MnO 2 and activated carbon as the positive and negative electrodes exhibits high specific capacitance (105.5 F g ?1 at 0.5 A g ?1 and 78.5 F g ?1 at 10 A g ?1) with excellent rate capability, achieves a maximum energy density of 43.9 Wh kg ?1 at a power density of 408 W kg ?1, and has high stability, whereby the ASC retains 81.4 % of its initial capacitance at a current density of 5 A g ?1 after 4000 cycles. Therefore, the NHCSs@MnO 2 electrode material is a promising candidate for future energy‐storage systems. 相似文献
12.
Nitrogen‐enriched porous nanocarbon, graphene, and conductive polymers attract increasing attention for application in supercapacitors. However, electrode materials with a large specific surface area (SSA) and a high nitrogen doping concentration, which is needed for excellent supercapacitors, has not been achieved thus far. Herein, we developed a class of tetracyanoquinodimethane‐derived conductive microporous covalent triazine‐based frameworks (TCNQ‐CTFs) with both high nitrogen content (>8 %) and large SSA (>3600 m 2 g ?1). These CTFs exhibited excellent specific capacitances with the highest value exceeding 380 F g ?1, considerable energy density of 42.8 Wh kg ?1, and remarkable cycling stability without any capacitance degradation after 10 000 cycles. This class of CTFs should hold a great potential as high‐performance electrode material for electrochemical energy‐storage systems. 相似文献
13.
We report effective solution‐processed chemical p‐type doping of graphene using trifluoromethanesulfonic acid (CF 3SO 3H, TFMS), that can provide essential requirements to approach an ideal flexible graphene anode for practical applications: i) high optical transmittance, ii) low sheet resistance (70 % decrease), iii) high work function (0.83 eV increase), iv) smooth surface, and iv) air‐stability at the same time. The TFMS‐doped graphene formed nearly ohmic contact with a conventional organic hole transporting layer, and a green phosphorescent organic light‐emitting diode with the TFMS‐doped graphene anode showed lower operating voltage, and higher device efficiencies (104.1 cd A ?1, 80.7 lm W ?1) than those with conventional ITO (84.8 cd A ?1, 73.8 lm W ?1). 相似文献
14.
A facile microwave method was employed to synthesize NiCo 2O 4 nanosheets as electrode materials for lithium‐ion batteries and supercapacitors. The structure and morphology of the materials were characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller methods. Owing to the porous nanosheet structure, the NiCo 2O 4 electrodes exhibited a high reversible capacity of 891 mA h g ?1 at a current density of 100 mA g ?1, good rate capability and stable cycling performance. When used as electrode materials for supercapacitors, NiCo 2O 4 nanosheets demonstrated a specific capacitance of 400 F g ?1 at a current density of 20 A g ?1 and superior cycling stability over 5000 cycles. The excellent electrochemical performance could be ascribed to the thin porous structure of the nanosheets, which provides a high specific surface area to increase the electrode–electrolyte contact area and facilitate rapid ion transport. 相似文献
15.
A simple hydrothermal method has been developed to prepare hexagonal tablet precursors, which are then transformed into porous sodium‐doped Ni 2P 2O 7 hexagonal tablets by a simple calcination method. The obtained samples were evaluated as electrode materials for supercapacitors. Electrochemical measurements show that the electrode based on the porous sodium‐doped Ni 2P 2O 7 hexagonal tablets exhibits a specific capacitance of 557.7 F g ?1 at a current density of 1.2 A g ?1. Furthermore, the porous sodium‐doped Ni 2P 2O 7 hexagonal tablets were successfully used to construct flexible solid‐state hybrid supercapacitors. The device is highly flexible and achieves a maximum energy density of 23.4 Wh kg ?1 and a good cycling stability after 5000 cycles, which confirms that the porous sodium‐doped Ni 2P 2O 7 hexagonal tablets are promising active materials for flexible supercapacitors. 相似文献
16.
Heteroatom doping is an effective method to adjust the electrochemical behavior of carbonaceous materials. In this work, boron‐doped, carbon‐coated SnO 2/graphene hybrids (BCTGs) were fabricated by hydrothermal carbonization of sucrose in the presence of SnO 2/graphene nanosheets and phenylboronic acid or boric acid as dopant source and subsequent thermal treatment. Owing to their unique 2D core–shell architecture and B‐doped carbon shells, BCTGs have enhanced conductivity and extra active sites for lithium storage. With phenylboronic acid as B source, the resulting hybrid shows outstanding electrochemical performance as the anode in lithium‐ion batteries with a highly stable capacity of 1165 mA h g ?1 at 0.1 A g ?1 after 360 cycles and an excellent rate capability of 600 mA h g ?1 at 3.2 A g ?1, and thus outperforms most of the previously reported SnO 2‐based anode materials. 相似文献
17.
Herein, we describe a simple two‐step approach to prepare nickel phosphide with different phases, such as Ni 2P and Ni 5P 4, to explain the influence of material microstructure and electrical conductivity on electrochemical performance. In this approach, we first prepared a Ni–P precursor through a ball milling process, then controlled the synthesis of either Ni 2P or Ni 5P 4 by the annealing method. The as‐prepared Ni 2P and Ni 5P 4 are investigated as supercapacitor electrode materials for potential energy storage applications. The Ni 2P exhibits a high specific capacitance of 843.25 F g ?1, whereas the specific capacitance of Ni 5P 4 is 801.5 F g ?1. Ni 2P possesses better cycle stability and rate capability than Ni 5P 4. In addition, the Fe 2O 3//Ni 2P supercapacitor displays a high energy density of 35.5 Wh kg ?1 at a power density of 400 W kg ?1 and long cycle stability with a specific capacitance retention rate of 96 % after 1000 cycles, whereas the Fe 2O 3//Ni 5P 4 supercapacitor exhibits a high energy density of 29.8 Wh kg ?1 at a power density of 400 W kg ?1 and a specific capacitance retention rate of 86 % after 1000 cycles. 相似文献
18.
In this work, green synthesis of cobalt doped titanium dioxide (Co‐TiO 2) has been carried out in aqueous medium using gelatin. The Co‐TiO 2 particles have been characterized using transmission electron microscopy (TEM), X‐ray diffraction (XRD), energy dispersive X‐ray (EDAX), FT‐IR spectroscopy and voltammetry techniques. XRD results show pure Co‐TiO 2 and TiO 2 powders with average crystallite size about 12 nm and 15 nm, respectively. Co loaded in TiO 2 hasn't influence crystalline structure. Moreover, efficient Co‐TiO 2‐based anode was fabricated by casting of the Co‐TiO 2 solution on glassy carbon electrode (Co‐TiO 2/GCE). The electrocatalysis of oxygen evolution reaction (OER) at Co‐TiO 2/GCE has been examined using linear scanning voltammetry (LSV) in alkaline media. The OER is significantly enhanced at Co‐TiO 2/GCE, as demonstrated by a negative shift in the LSV curve at the Co‐TiO 2/GCE compared to that obtained at the unmodified one. The value of energy saving of oxygen gas at a current density of 5 mA cm ?2 is 12.6 kW h kg ?1. The low cost as well as the marked stability of the modified electrode make it promising candidate in industrial water electrolysis process. 相似文献
19.
In this work we explore the electrocatalytic activity of nanocomposites of reduced sulphur doped graphene oxide nanosheets (rSDGONS) and cobalt phthalocyanine (CoPc) or cobalt tetra amino phthalocyanine (CoTAPc) towards hydrogen peroxide. Transmission electron microscopy, scanning electron microscopy, X‐ray photon spectroscopy, X‐ray diffraction, chronoamperometry, linear scan voltammetry and cyclic voltammetry were used to characterize the nanocomposites. Nanosized CoPc showed superior (in terms of currents) electrocatalytic oxidation and reduction of hydrogen peroxide compared to CoTAPc nanoparticles (CoTAPc NP ). The lowest detection limit was obtained for hydrogen peroxide oxidation on electrodes modified with CoPc NP ‐rSDGONS at 1.49 µM. The same electrode gave a high adsorption equilibrium constant of 1.27×10 3 mol ?1 and a Gibbs free energy of ?17.71 kJ/mol, indicative of a spontaneous reaction on the electrode surface. 相似文献
20.
An advanced supercapacitor material based on nitrogen‐doped porous graphitic carbon (NPGC) with high a surface area was synthesized by means of a simple coordination–pyrolysis combination process, in which tetraethyl orthosilicate (TEOS), nickel nitrate, and glucose were adopted as porogent, graphitic catalyst precursor, and carbon source, respectively. In addition, melamine was selected as a nitrogen source owing to its nitrogen‐enriched structure and the strong interaction between the amine groups and the glucose unit. A low‐temperature treatment resulted in the formation of a NPGC precursor by combination of the catalytic precursor, hydrolyzed TEOS, and the melamine–glucose unit. Following pyrolysis and removal of the catalyst and porogent, the NPGC material showed excellent electrical conductivity owing to its high crystallinity, a large Brunauer–Emmett–Teller surface area ( SBET=1027 m 2 g ?1), and a high nitrogen level (7.72 wt %). The unusual microstructure of NPGC materials could provide electrochemical energy storage. The NPGC material, without the need for any conductive additives, showed excellent capacitive behavior (293 F g ?1 at 1 A g ?1), long‐term cycling stability, and high coulombic efficiency (>99.9 % over 5000 cycles) in KOH when used as an electrode. Notably, in a two‐electrode symmetric supercapacitor, NPGC energy densities as high as 8.1 and 47.5 Wh kg ?1, at a high power density (10.5 kW kg ?1), were achieved in 6 M KOH and 1 M Et 4NBF 4‐PC electrolytes, respectively. Thus, the synthesized NPGC material could be a highly promising electrode material for advanced supercapacitors and other conversion devices. 相似文献
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